Electronic switching devices must be protected from excessive power switching application, operation at a switching frequency greater than the maximum average frequency must be limited to short periods of time. The short periods of operation are defined as burst periods. The burst period must decrease as the switching frequency increases. A graph of a typical operating curve is shown in FIG. 1.
In the illustrative typical example, reflected by the operating curve of FIG. 1, it will be observed that, at the operating frequency of 300 Khz, the burst period should be infinite for continuous operation of a high frequency switch. Examples of high frequency switches, to which the present invention pertains, include a traveling wave tube (TWT) modulator and a Q switch modulator. At frequencies greater than the operating point, the burst period will decrease to a minimum of approximately 8.6 .mu.s at 5 Mhz. For the example given, the latter mentioned frequency is the maximum switching frequency at which the typical high frequency switch should operate. Above that frequency, power dissipation can destroy the switch. A typical burst requirement for a high frequency switch is operation at an elevated frequency of 1.1 Mhz for 39 .mu.s. The input of a typical high frequency switch (command input) is a variable frequency and duty cycle pulse train.